Pediatric Dental Health

November 1, 2001

Should Children Have White Dental Fillings?see
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The restoration of primary teeth is an important component of children’s oral
health care. Many parents want to know if their children should have white
dental restorations. The answer depends upon many factors.

Amalgam has been the material of choice for many years in the restoration of
children’s teeth. Recently, however, tooth-colored dental restorative
materials have become popular for use in children’s teeth. A major reason is
the growing demand for esthetic dental restorations.

WHAT KINDS OF TOOTH-COLORED MATRIALS ARE AVAILABLE?

There are basically three types of tooth-colored materials which are used
to restore posterior primary teeth: resin-modified glass ionomers,
composites, and compomers.

Resin-modified glass ionomers (RMGI) are glass ionomer cements to which a
resin has been added for strength.

Composites are a tooth colored material consisting of two main components:
a matrix and a filler.

Compomers are polyacid-modified resin composites. They consist of a
single, hydrophobic resin which is filled with acid-leachable glass
particles similar to those found in glass ionomer cements.

HOW DO TOOTH COLORED RESTORATIONS WORK?

Conventional glass ionomers are derived from aqueous polyalkenoic acid and
a glass component. When the powder and liquid are mixed together, an acid
base reaction occurs. Resin-modified glass ionomers (RMGI) work by the
fundamental acid-base reaction, which is supplemented by a second resin
polymerization reaction.

In addition to its micro-mechanical adhesion to dentin, enamel, and
cementum - RMGI chemically bonds to the calcium in dentin and enamel.

RMGI also releases fluoride. Fluoride is released from glass ionomer and
RMGI not only when it is placed, but also after fluoride treatments and
brushing with fluoride toothpaste. This is because glass ionomer acts as a
fluoride reservoir.

Finally - although the shear bond strength of RMGI to tooth structure is
only 4-5 mPa, this restorative material succeeds because its coefficient of
thermal expansion is very close to that of a tooth. In other words, when the
tooth expands, the RMGI expands in a like fashion.

Composites are composed of a resin matrix, an inorganic filler, and an
interfacial phase. The matrix provides the framework, and the filler imparts
its mechanical properties onto the composite.

Compomers are similar to composites. They have a wear rate about 3 times
that of a composite, however. In addition, compomers require placement of a
bonding agent to ensure adequate retention to dentin surfaces.

WHAT ARE THE ADVANTAGES OF A TOOTH-COLORED RESTORATION?

Resin-modified glass ionomer (RMGI) is a tooth-colored material that bonds
chemically to the tooth, and releases fluoride for a relatively long period
of time.

Finally – less tooth enamel needs to be removed by the dentist when an
adhesive, tooth-colored restoration is placed in a tooth, than when an
amalgam restoration is placed.

WHAT ARE THE DISADVANTAGES OF A TOOTH-COLORED RESOTRATION?

The time required for a dentist to place a tooth-colored restoration is
usually greater than that required for an amalgam restoration.

A tooth-colored restorative material is not as forgiving as dental amalgam
insofar as the dentist’s clinical technique is concerned. Contamination of
the cavity preparation may occur before the restorative material has been
placed.

A tooth-colored restoration is not as durable as an amalgam restoration.
This is because its compressive and tensile strengths are not as great as
that of an amalgam restoration.

A composite restoration often “fails” because new caries can develop
underneath the filling (recurrent caries).

CLINICAL TECHNIQUE FOR PLACING RESIN-MODIFIED GLASS IONOMER:

Provide adequate local anesthesia.

The operative field must be kept clean and dry during insertion of the
resin-modified glass ionomer (RMGI). Therefore, placing a rubber dam is
highly recommended.

Pre-wedging of the tooth during tooth preparation will protect the
gingival tissue, as well as the interdental rubber dam. Pre-wedging also
makes it easier to achieve contact with the adjacent tooth after the
restoration has been inserted.

The matrix band should be burnished to the proper contour before placing
the RMGI.

Powder and liquid components of RMGI may be hand-spatulated using the
highest powder/liquid ratio, and ensuring that all of the powder is
sufficiently wetted by the acid solution.

Incremental placement of the RMGI is recommended to prevent voids. RMGI is
best placed into the cavity preparation using a syringe tip such as the
Centrix. The mixed RMGI is syringed into place starting from the bottom of
the preparation. Once the preparation is overfilled, the material can be
compressed onto the tooth using a gloved finger.

The RMGI cement is light-cured for forty seconds.

All glass ionomer cements should be kept free of moisture and
contamination during the initial setting period – which can last 3-4
minutes if self-cure material is used.

Finally, trim the restoration and establish final contours using finishing
burs. Check the occlusion.

CONCLUSION:
Dental esthetic demands have increased during the last decade. As the
strength and durability of tooth-colored restorative materials continue to
improve, they will be used more frequently to restore the posterior teeth of
children. Resin-modified glass ionomer (RMGI) may be useful for the
restoration of children’s posterior teeth because: it does not require a
lengthy etching and bonding procedure, it releases fluoride, it bonds
directly to dentin and enamel, and its coefficient of thermal expansion is
similar to that of natural tooth. Nevertheless, stainless steel crowns may
be more appropriate to use when restoring the proximal carious lesions in a
child who has a high risk for caries disease.

An article in the Journal of the American Dental Association discussed
the success of resin-modified glass ionomer (RMGI) cement as a restorative
material in primary teeth. This study provided data from one practitioner
who was the owner of the practice. The 306 children who were studied had a
total of 864 RMGI restorations place by the author of the study. The overall
success rate for two-surface, Class II posterior restorations was 93.3
percent over an average of 4 years and one month’s time in the mouth.